I work at a cinema and boy, let me tell you. There are 28 movies to be released this year specifically designed with elements of 3D viewing, and our cinema is picking up 22 of them. Among them are Harry Potter and the Deathly Hallows pt.1, How to train your dragon, Clash of the Titans, Prince of Persia and Toy Story 3.
I only just got back from seeing clash of the titans in 2D (disappointing really) and i noticed that there were several scenes that were obviously made for 3D viewing. My problem is that when you opt to see the film in 2D for whatever reason, you tend to really notice the CGI-FX and it feels like its reducing the quality of the film. I understand for entirely animated films like toy story 3 and how to train your dragon being able to fully utilise the 3D projection, but when its movies like alice in wonderland or Clash of the titans, only a few scenes are necessarily using the 3D capabilities, leaving the rest as normal viewing, except you're straining your eyes for no reason.
I must admit however, 3D live action films can be grand and engaging, when the effort to include as much of the 3D capability is done so. Avatar is a good example of animated/live action 3D that isn't blatantly obvious when viewed in 2D.
My other issue is the fact that since no single model of 3D glasses can be agreed upon, nor the design of the screens, so every screen will be different, and i suspect that the viewing experience will differ from cinema to cinema, which may give the more expensive cinema an unfair advantage over the budget kind as the more expensive cinema can afford the best quality and most expensive glasses and screens.
And finally, as this will affect gamers, tv viewers, at home movie buffs and theatre goers, the 3D glasses will always be present, well for at least another 10 years, so if you already wear glasses, good luck wearing 2 pairs, and if you get headaches from watching with the glasses? There is nothing that can be done except watching the film in 2D, and for now choosing between 2D viewing and 3D viewing has always been our right, but soon enough there will be "3D ONLY" movies coming up. So you better hope if you don't like 3D, that the movie you've been waiting for will be in 2D too.